Air conditioner fan stops blowing as hard

[Jon657]

When I was driving across country (through the desert), my airconditioner fan would stop blowing as hard as it should on high (air was still cold) so I would turn it off for a few minutes and it and re-start it and it would be fine. I had to do this about every 100 miles or so. I havent had any problems since my cross country trip except one time the other day when it did it on a 45 minute drive. Otherwise, the thing blows cold and hard everyother time.
Any idea what this is? Is the fan freezing up or overheating or what? I dont smell anything burning and as many times as it happened, I think it would have quit all together if it was overheating.
Any ideas?
Thanks,
Jonathan

[colinb67]

I would say either the resistor or the switch it self, maybe even the connector at the blower motor. Could be that they have a little resistance going and then it starts getting hot. Thus slowing the fan spped down. The best thing to do is test the voltage at the blower motor plug. On high it should be 12v (maybe a bit higher). when you turn the fan switch down the voltage to the motor is dropped to lets say 9v on med then 7v on low. So if the switch is on high and you do not have 12v at the connector you need to trace the wiring to the next junction and test voltage there. Continue until you find where the voltage drop is and there your problem will be.